That's an impressive man-made tunnel, but not as impressive as a Canadian ice cave, formed by mother nature.
This cool creation in a New Brunswick forest has been dubbed the Midland Ice Caves. The wall of ice forms naturally every year; made one drop at a time from a nearby brook that drips off the edge of a cliff.
Human hands help out a little by creating a hole so people can get through the ice wall. The caves draw more than 400 visitors every weekend.